In a chopper you still need to aviate, navigate communicate and if you were just in communication with someone you could make a call possibly or you could have 121.5 selected for transmitting and switch to Area when a call is required.
switching on your PLB prior to impact is great if possible but it has a 60 second delay before transmitting so must survive the impact to help at low levels.
It is up to the pilot to determine the best frequency to make a emergency call on based on best chance of being heard.
If as is required all aircraft monitor 121.5, then unless you are currently chatting with someone on a frequency obviously the best emergency frequency based on chance of being heard would be 121.5. Simply I think, many have found that boring and prefer some other channel that is not in the interest of safety.